package com.kuang.response;


import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.URLEncoder;

/**
 * 下载文件流程
 * 1.要获取下载文件的路径
 * 2.下载的文件名是啥
 * 3.设置想办法让浏览器能够支持下载我们需要的东西
 * 4.获取下载文件的输入流
 * 5.创建缓冲区
 * 6.获取OutputStream对象
 * 7.将FileOutputStream流写入buffer缓冲区
 * 8.使用OutputStream将缓冲区中的数据输出到客户端!
 */
@WebServlet("/fileDown")
public class FileServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.要获取下载文件的路径
        String realPath = "E:\\IdeaProjects\\Work1\\java-web\\servlet-02\\src\\main\\resources\\1.png";
//        String realPath = this.getServletContext().getRealPath("/1.png");
        System.out.println("下载文件的路径:" + realPath);
        //2.下载的文件名是啥
        String fileName = realPath.substring(realPath.lastIndexOf("//") + 1);
        //3.设置想办法让浏览器能够支持(Content-Disposition)下载我们需要的东西
        resp.setHeader("Content-Disposition","attachment;filename" + URLEncoder.encode(fileName, "UTF-8"));

        //4.获取下载文件的输入流
        FileInputStream in = new FileInputStream(realPath);
        //5.创建缓冲区
        int len = 0;
        byte[] buffer = new byte[1024];
        //6.获取OutputStream对象
        ServletOutputStream out = resp.getOutputStream();
        //7.将FileOutputStream流写入buffer缓冲区
        while ((len = in.read(buffer)) > 0) {
            out.write(buffer, 0, len);
        }
        in.close();
        out.close();
        //8.使用OutputStream将缓冲区中的数据输出到客户端!


    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}
